Upper surfaces of Little Foot bones are exposed, after a lengthy and careful excavation process. Photo: Paul Myburgh

The paleontological detective work has been in process for 20 years, since a tiny ankle bone matched a tiny outcropping in a deep dark cave in South Africa.

Now, the “Little Foot” fossilized skeleton – the most complete and oldest Australopithecus yet discovered – has been unveiled to the world, said the University of the Witwatersrand.

The work by paleontologist Ron Clarke has taken painstaking decades, and the scientific publications outlining their findings on our earliest hominid ancestor will be appearing over the next year.

“This is one of the most remarkable fossil discoveries made in the history of human origins and it is a privilege to unveil a finding of this importance today,” said Clarke, in a school statement.

The trail to the fossil, which is 3.67-million-years-old, began in 1994. An ankle bone and other fragments of the skeleton from the parts of the lowest legs were found in rock blasted by lime miners from a Sterkfontein cave about 40 kilometers outside Johannesburg in the early 20th century, according to Clarke.

Clarke figured there could be more down in the deep caves. He sent his assistants Stephen Motsumi and Nkwane Molefe inside with casted replicas of the bones to try and find a match somewhere inside the cave. After a full day-and-a-half in July 1997, they found where the bits fit.

The bones they gradually began to delineate were soft, powdery and flaky – but sealed in a natural concrete-like rock called breccia, Clarke said. The digging and clearing lasted through 2012 – and involved use of such precision tools as an AirScribe chisel to carefully remove the rock form the fossil.

“The process required extremely careful excavation in the dark environment of the cave,” recounted Clarke. “Once the upward-facing surfaces of the skeleton’s bones were exposed, the breccia in which their undersides were still embedded had to be carefully undercut and removed in blocks for further cleaning in the lab at Sterkfontein.”

Clarke was the right person for the exacting job, said Robert Blumenschine, the chief scientist of the Paleontological Scientific Trust (PAST), an NGO which helped fund the ongoing years of work.

“He (Clarke) is one of the world’s very best excavators of hominid fossils,” said Blumenschine. “I like to refer to Ron as a ‘paleo-surgeon.’”

The new skeleton, which appears to have an intact skull and wide swaths of other bones from the images provided by Witwatersrand, is remarkably more complete than other comparative fossils. For instance, the famed Lucy is younger, at 3.2-million-years-old, and has only fragments from the skull and only small parts of the legs. Even those limited existing remains have allowed scientists to fill in many gaps in the hominid family tree. The discovery of only a partial jaw in 2011 in Ethiopia also led to the naming of a new species in 2015.

Stephen Motsumi, Ron Clarke and Nkwane Molefe. Photo: Paul Myburgh